The development of the mammalian gustatory sense will be investigated to determine the time of onset of function and to describe changes in taste function as the sensory system develops. Fetal, newborn and adult sheep will be used in physiological and behavioral studies. To establish when the peripheral taste system begins to function, electrophysiological recordings will be made of neural responses from the primary taste afferents from the time of taste bud appearance throughout morphological development. The extent to which the fetus can perceive the taste of its liquid environment, the amniotic fluid, will be assessed. As a measure of perception, the swallowing activity of the fetus will be continuously monitored using an electromagnetic flow transducer implanted in the fetal esophagus. Attempts will be made to modify normal swallowing by injecting taste stimuli into the amniotic fluid. These experiments will detail the functional development of the sense of taste and will elucidate the possible biological significance of the gustatory sense during intrauterine life. Bibliographic references: Mistretta, C.M. and R.M. Bradley. 1975. Taste and swallowing in utero. Brit. Med. Bull. 31:80-84; Bradley, R.M. and C.M. Mistretta. 1975. Fetal sensory receptors. Physiol. Rev. 55.